1. Field of the Invention
This invention relates to an underwater scooter that can travel on the surface of the water or underwater.
2. Description of the Related Art
Underwater scooters that can travel on the surface of the water or underwater under the control of an operator (diver) have been proposed in the past. This type of underwater scooter typically generates thrust by an internal combustion engine or electrical motor that drives a propeller as the drive power unit (power source). Moreover, it is provided with handle grips that are held onto by the operator, in a constitution such that it tows an operator holding onto the grips and assists their forward motion, as taught in U.S. Pat. No. 5,394,820 and Japanese Patent Publication No. Hei 4(1992)-17832, for example.
The output shafts of internal combustion engines or electric motors mounted on the underwater scooters are usually directly connected to the propellers Therefore, in order to stop the running of the underwater scooters, the operation of the engine or motor must be made off.
Meanwhile, most engines mounted on the underwater scooters are started by pulling recoil starters hard. Since the operator's posture is likely to be unstable on the surface of the water or underwater, it is difficult for the operator to re-start the engine once stopped, thereby rendering the operation to resume running of the scooter tedious.
On the other hand, the electric motors are easily started on even on the surface of the water or underwater by simply turning the switch on. However, if the electric motor is used as the drive power unit of the underwater scooter, if a long distance travel is desired, the capacity of battery must be increased. This is disadvantageous in terms of weight, when compared to the case that the engine is used as the drive power unit, where the same purpose is achieved by increasing fuel tank capacity. Thus, when the electric motor is used and a distance of travel is increased, a heavier size of power source is unavoidable.